In the making of an aspherical or non-rotationally symmetrical lens, such as lenses with toroidal surface or free-form surfaces, one generally uses tools and polishing heads that are smaller than the surface of the lens being machined, so-called zone polishing tools.
In zone machining, the tool or the polishing head is guided over the surface, while polishing compound is placed on the areas of the lens surface being machined that are not covered by the tool, which then works its way in between the polishing tool and the lens surface being machined, thereby improving the polishing performance. In order to adapt the polishing head to the shape of the surface being machined, this is mounted by a ball and socket joint and can be tilted. Moreover, the polishing head has an elastic backing layer for the polishing foil, so that a local deformation of the polishing head is possible for an adapting to the shape.
Such a polishing tool is known from DE 10 2004 062 319 B3. This describes a polishing device for optical lenses with a seat having an axis of rotation X for arrangement on a polishing machine and a collar arranged on the seat for the rotational driving of a tool holder or polishing head holder arranged on the collar, wherein the tool holder is guided by and tilted by a guide piston, coaxially mounted in the seat and able to move in the direction of the rotational axis X.
Moreover, a polishing device for the polishing of optical lenses is known from DE 10 2008 061 267 A1. The polishing device has a tilting base piece for direct or indirect holding of a polishing pad, wherein the base piece is connected to a polishing spindle for purposes of rotary drive and a rotary leadthrough is provided for purposes of feeding of polishing compound, being arranged at least partly opposite the polishing spindle in relation to the base piece. The leadthrough is supplied from the outside by means of a hose connection via a stationary reservoir of polishing compound, the hoses being attached to the nonturning part of the leadthrough, even though this is likewise tilted during the process.
A polishing device is known from DE 10 2009 036 981 A1 for the polishing of optical lenses, with a tilting base part, for the direct or indirect holding of a polishing pad, wherein the base piece has a spherical cap for placement on a spherical head of a polishing spindle and the base piece is coupled for rotary drive to a spindle shaft of a polishing spindle by a connection piece, wherein the spherical cap is designed as a separate bearing part and it is arranged in the base piece.